Hydraulic lift jack



Feb. 16, 1954 s J PEHRSSQN 2,569,423

HYDRAULIC LIFT JACK 2 Sheets-She et 1 Filed April 24, 1952 54 6 55 7 55 5E y 57 INVENTOR.

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4770B JEYS Feb. 16, 1954 Filed April 24, 1952 5. J. PEHRSSON HYDRAULIC LIFT JACK .lllm

2 Sheets-Sheet 2 INVENTOR.

ATTOFMEYS Patented Feb. 16, 1954 HYDRAULIC LIFT JACK Sven J. Pehrsson, Elyria, Ohio, assignor, by mesne assignments, to The Colson Corporation, Elyria, Ohio, a corporation of Ohio Application April 24, 1952, Serial No. 284,102

1 Claim.

This invention relates to wheeled lift jacks or truck jacks and in particular to hydraulic lift jacks of the type designed to be placed under the front part of a skid or platform truck to elevate and lower, support and transport same from place to place.

It is among the objects of my invention to provide an hydraulic lift truck jack that may be easily and certainly applied to, used with and detached from a platform truck with a maximum of convenience, safety, stability and maneuverability and may also be conveniently handled, stored and received apart from the truck with which it has its ultimate use. Another object is to provide an hydraulic lift jack which may be operated to lower as well as raise loads quickly and gently with a minimum of effort and maximum safety for the operator and load. Another object is to provide an hydraulic lift jack with operating controls conveniently located thereon for ready access to and efficient use by the operator. Another object is to provide an hydraulic lift jack that is stable and balanced under load and is easy to steer. Another object is to provide an hydraulic lift jack that is simple in design, economical to produce and rugged in construction.

These and other objects of my invention will appear from the following description of a preferred embodiment thereof, reference being had to the accompanying drawings in which Figure 1 is a side elevation of my improved lift jack shown in the elevated position supporting the front portion of a skid; Figure 2 is an enlarged elevation of the jack with a portion thereof cut away to show details of construction; Figure 3 is a plan view of the jack; Figure 4 is a transverse section of the jack taken on the line 4-4 of Figure 3; and Figure 5 is a schematic drawing showing the hydraulic circuit and control valve which form a part of the jack apparatus.

The type of lift jack which embodies the present invention is designed to be used with a conventional skid or platform truck I (see Figure 1) which has a pair of rear wheels 2 and stationary front legs 3 on either side of the skid adapted to support loads when the jack is disconnected from the skid. The front end of the skid also has a downwardly extending king pin 4 located midway between the sides of the skid; the king pin l is adapted to be engaged by the jack in the well known manner for lifting the skid and moving it from place to place. In the description which follows the right hand end of the jack and skid as viewed in Figure 1 is referred to as the front end while the opposite or left hand end is referred to as the rear end of the apparatus.

Referring to the drawings, the jack unit comprises a carriage C on which is mounted a pump unit P and an hydraulic lift mechanism or ram R. The carriage C has a rigid preferably channel shaped chassis having a substantially hori- Zonta1 base part 5 and laterally spaced vertically extending side walls 6, 6 which extend the full length of the carriage. The side walls have transverse apertures 1, 7 formed therein at the rear end of the carriage, which apertures are adapted to receive and support the main load bearing axle 8 on which heavy duty load supporting, preferably rubber-tired, wheels 9, 9 are journalled. In order to support the front end of the carriage l, I provide a pair of transversely extending channel shaped arms I0 preferably welded at their inner ends II to the side walls 6, 6 of the carriage, each arm I ll carrying at its outer end a vertically pivotal caster assembly l2 which includes, a caster wheel l3 arranged to pivot about a vertically disposed stem l4. Each caster preferably is longitudinally aligned with the center plane of the rear wheel 9 on the same side of the carriage. Thus the carriage C is supported on four wheels that are symmetrically arranged about the central longitudinal and transverse axes of the carriage, which arrangement insures and enhances stability of the apparatus under load as well as under no load conditions.

In order to permit the carriage to be guided conveniently and accurately into position under the skid preparatory to moving same as well as to provide a convenient means for pulling and maneuvering the loaded skid, an elongated handle H is provided. The lower end of the handle H preferably has two laterally spaced legs [5 which are pivotally connected at their respective ends 16 to a horizontal transverse pin I'I; pin I! extends through the side walls 6, 6 at a point which is offset forwardly from the load lifting mechanism or ram R. The opposite ends N3 of legs [5 are connected to an elongated handle body l9 provided with a handle bar 20 at its free end for grasping by the operator. The handle is capable of being pivoted about pin I! from a position of rest on the floor to an upright position with the legs leaning against the transverse plate 3| which extends across the rear end of the carriage. I

The mechanism I employ to elevate and lower the skid to and fromthe operative or transportable position preferably consists of an hydraulic system comprising a ram mechanism R which actually does the work of lifting and lowering the load and a ram actuating mechanism or pump P by which fluid under high pressure is pumped to and withdrawn from the ram. The ram R consists of a cylinder 24 in which a piston 25 is disposed to move in a vertical direction in response to fluid pressure in the ram cylinder. The ram is located in the longitudinal axis of the carriage C closely adjacent and immediately forward of the axle 8 between the main load bearing wheels 3, 9 and has its lower end securely seated in a central opening 26, see Figure 4, in the carriage base 5, the ram cylinder having an annular shoulder 28 formed thereon engaging the base for supporting the load. The upper end of the cylinder 24 has an upwardly facing shoulder 36. A transversely extending plate 31 detachably secured by bolts 32 to the sides 6, 6 of the carriage has a central aperture 33 arranged to fit around the ram piston '25 like a sleeve to guide the piston during its vertical movements and to prevent any rocking or like movement of the ram unit. The plate 3| also is disposed to engage and exert a downward pressure against shoulder on the top of the ram cylinder to tightly seat the bottom of the cylinder in the base..

In order that the ram piston 25 will operably engage the king pin 4 of the skid, a king pin socket assembly is detachably secured to the top of the piston by means of a threaded stud 35 disposed in a tapped hole 36 in the top of the ram piston. The socket assembly 34 is described in full detail in Patent No. 2,184,455 issued to Johnson. It is suflicient here to point out that socket assembly 34 has a cylindrical recess 31 adapted, when the ram piston 25 is raised as indicated in dot-dash lines in Figures .2 and 4, to receive king pin 4 of the skid; anti-friction means, not shown, are provided within the socket assembly to permit rotation of the king pin 4 relative to the carriage and thus to facilitate steering of the jack and skid.

Fluid under pressure to actuate the ram R for raising and'lowering the skid is pumped from the pump unit P which preferably is positioned centrally on the front portion of the carriage base 5; the pump unit P is secured to the jack base by bolts and nuts 45' which fasten flanges 45 on the pump casing to the base. The pump unit P comprises a pump 53 (see Figure 5), a sump 54 and a suitable check valve 55 for controlling the flow of fluid between the pump unit P and the ram mechanism R. The valve 55 is mechanically connected by appropriate means indicated by a dot-dash line 56 to an operating lever 51 located at the forward end of pump unit P where it is conveniently accessible. When the lever 51 is placed in one position, say the position shown in solid lines in Figure 5, the valve 53 permitsflow of fluid in one direction only, for example, in the direction from the pump unit P to the'ram R, for elevating or raising the load. Thus, in order to raise the ram piston 25 and the load, fluid is pumped from sump 54 through conduit 53 to pump 53, through conduit 59, check valve 55, conduit and finally into the ram cylinder 24. Check valve prevents backward or reverse flow of fluid in the system during the load lifting cycle.

In order to lower the load, lever 51 in the front of the jack is moved to its other operative position indicated in dot-dash lines in Figure 5, whence the mechanism of valve 55 is changed to permit the reverse flow of fluid in the system; that is, fluid will pass from ram cylinder 24 under pressure of the load, through conduit 60, check valve 55 and through conduit 6| to the sump 54.

In order to actuate the pump 53 to pump fluid to the ram to elevate the load, a foot actuated lever or treadle bar 63 is connected to the piston 53a of pump 53 by rod 64. The treadle 63 is mounted for pivotal movement in a vertical plane about a transverse pin 65 carried by laterally spaced vertically extending flanges 66 on the top 7 of the pump unit P. The treadle is operably connected to the piston rod 64 at 61 and has a rearwardly extending portion 68 connected by spring to pin l1; spring 39 urges the pedal and thus piston 53a. to the upper limit of the pumping intake stroke. The forwardly extending portion of treadle bar 33 is bent downwardly as indicated at 15 over the front of the pump unit P and terminates at its front end in a foot pedal 11. When the operator presses down on the foot pedal 1|, the pump 53 is actuated and fluid is forced under pressure to the ram R, to raise the load.

The construction of my hydraulic truck lift jack is particularly advantageous because it is balanced and stable under load. The ram is located immediately adjacent the load bearing axle 5 so that practically the full load of the skid is carried by the main support wheels 9. The moment of force created by the offset between the ram R and axle 8 is supported by the forward caster wheels 53 which, being pivotally mounted on their supporting arms it do not in any way interfere with the steering movements of the jack, and on the contrary give stability for all movements of the jack and load. The jack is sturdy and rugged and capable of lifting and transporting heavy loads without danger of tipping or unbalancing the load. This jack is also convenient to operate since the controls, that is, valve operatinglever 51, the pump treadle 63 and the handle H, are located at the front end of the carriage within easy reach of the operator; also maneuverability and steering are enhanced by reason of the novel construction of my jack and the load distribution afforded thereby.

While I have described and illustrated a preferred form of my invention, other changes and modifications thereto will occur to those skilled in the art who will come to understand the precepts of my invention, and. I do not intend to be limited in the scope of my patent to the particular form or forms of my invention herein specifically illustrated and described nor in any manner inconsistent with the extent to which my invention has promoted the art.

I claim:

An hydraulic lift jack comprising, a carriage having a base and spaced side walls connected to said base, a transversely extending axle at one end of said carriage supported by said side walls, wheels journalled on the ends of said axle, transversely extending arms at the other end of said carriage secured to said side walls, a caster assembly including a caster carried by each of said arms in longitudinal alignment with one of said wheels on the same side of the carriage, a ram having a piston movable in direction normal to said base, said ram being supported by said base along the longitudinal axis thereof adjacent said axle, a transverse plate detachably secured to said side walls, said plate engaging said ram remote from said base to secure same on said base and having a central opening through which said ram piston extends, the sides defining said opening engaging said piston to guide same in vertical movements, an hydraulic pumping unit detachably secured to said base and hydraulically connected to said ram, said pumping unit including a manually adjustable valve to control the direction of flow of fluid between said pumping unit and said ram, a valve control lever located at the other end of said carriage remote from said ram and operably connected to said valve, a treadle operably connected to said pump unit to pump fluid from said pump unit to said ram to raise said ram piston, said treadle extending from said other end of said carriage, and a pull handle 'pivotally connected to said carriage adjacent said ram, said handle extending beyond said other end of said carriage.

SVEN J. PEI-IRSSON.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,046,207 Lynt Dec. 3, 1912 1,713,344 Lewis May 14, 1929 1,852,544 Weaver Apr. 5, 1932 2,266,398 Quayle Dec. 16, 1941 2,582,896 Acton Jan. 15, 1952 

